9. General Anesthesia Flashcards
What are the stages of General anesthesia
Stage I= Analgesia
-From induction to loss of conciousness
Stage II= Stage of excitement
- From loss of conciousness to automatic breathing
- Breath-holding
- Vomiting
- Irregular respiration
Stage III= Surgical anesthesia (onset of automatic breathing to respiratory paralysis)
- Plane 1= From automatic breathing to loss of eye movement
- Plane 2= From loss of eye movement to partial paralysis of intercostal mm
- Plane 3= Complete paralysis of intercostal muscles
- Plane 4= Paralysis of the diaphragm
Advantages of General Anesthesia
- No need for LA
- Control over respiration and heart function
- Reduces awarness and recall
- Easily adaptable and rapidly administered and reversible
Disadvantages of GA
- Cost
- Pre-op patient management (need to be NPO)
- Requires increased complexity of care
- Malignant hyperthermia**
- NV, sore throat, nose bleed, headache
- Delayed return to normal mental function
What are the CNS effects of volatile anesthetics
- Changes in cognition recovery time= 24-36 hrs
- Psychomotor recovery= 24-36 hrs
- JAMA pediatrics kids that have had GA have less than 1/2% lower GPAs than kids that didn’t have GA
According to the FDA GA should be done for kids under the age of _ and for what other patient population
<3 y.o
-Pregnant (3rd trimester)
Respiratory effects of volatile anesthetics
- Increased PaCO2
- Decreased response to increase PaCO2 (central chemoreceptors)
- Deminished response to PaO2(peripheral chemoreceptors)
- Decreased tidal volume
- Increased respiration rate
- Net decrease in airway resistance (block effects of histamine)
- Apnea produced with greater depths
Volatile anesthetics result in lose of which muscles first? Diaphragm or intercostal
-intercostal
CV effects of volatile anesthetics
- Decreased arterial BP= decreased peripheral resistance and cardiac output
- Decrease O2 needs of the heart
- Reflex stimulation of SNS
- Sensitizes the myocardium to catecholamines (esp. halothane) –> cardiac dysrhythmias
For volatile anesthetics blood flow decreases to what organs and increases to what organs
Decreases
- Kidney
- Liver
- Gut
Increases
- Brain
- Muscle
- Skin
Renal effects of volatile anesthetics
decreased GFP and decrease in urine output
Endocrine effects of volatile anesthetics
- Not much effect with sevofluorane
- Decreased insulin secretion and tissue response to insulin
- Decreased testosterone
Neuromuscular effects of volatile anesthetics
-Muscle relaxation
Toxicities of volatile anesthetics
- Renal toxicity (metabolism of fluoride ions from halogenated hydrocarbons)
- Hepatotoxic (necrosis) -esp halothane
- Malignant hyperthermia
What is Malignant hyperthermia
-Ca2+ binds myosin and does dissociate –> chronic muscle contraction
Consequences of malignant hyperthermia
- -Constant muscle contraction (rigidity)
- Electrolyte imbalance
- Increased PaCO2
- Respiratory and metabolic acidosis
- Tachycardia
Advantages of both Desflurance and Sevoflurane
both are less toxic and have lowest solubilities (rapid onset and recovery) and they don’t sensitize the heart to catecholamines
Desflurane and sevoflurane have (high/low) Blood:gas partition coefficients
low
What is a disadvantages that desfluorane and sevoflurane share
MH triggers
What are the 4 steps in the GA technique
- Induction
- Intubation
- Maintenance
- Emergence
What is involved in induction
- Pre-oxygenation
- Inhalation anesthetics and IV induciton
- Sodium thipental + muscle relaxant
- Etomidate + muscle relaxant
- Propofol + mm relaxant
Describe the process of intubation
- Lift the patients head up and tilt back
- Laryngoscope
- Miller= straight and moves the epiglotis out of the way
- Macintosh= curved and moves the tongue forward at the volecula to move the epiglottis
People who are hard to intubate are
- Cellulitis (infection)
- Large necks
- Retrognathic mandible
- *Basically anyone with a compromised airway
What distance is used to judge the difficulty of intubation from patient to patient .
ear-to sternal notch
At what stage in GA should the intubation tube be removed
Stage I (not stage II –> laryngospasm)
For long cases the speed of recovery is (directly/indirectly) proportional to solubility
indirectly
